Congress is poised to vote on the biggest government intervention in the financial markets since the Great Depression, but it’s unlikely that any of the three senators vying for the White House will be there – even though all three have talked of little else for over a week.

Sen. John McCain (R- Ariz.) has no plans to return to Washington this week, even though on Monday he expressed discomfort with Treasury Secretary Henry Paulson’s trillion-dollar bailout plan and has offered his own rescue proposal.

“Sen. McCain is monitoring the situation closely,” said campaign co-manager Steve Schmidt on a conference call Monday. “We will see how this unfolds this week.”

McCain “retains his rights to evaluate it as it goes along and make a final decision,” said co-manager Rick Davis.

Sen. Barack Obama (D-Ill.) also looks like a no-show.

Senior Obama strategist Robert Gibbs said the campaign would be monitoring the process as it unfolds this week, but as of Monday, the campaign would not commit to Obama making the trip back to Washington – even though the bailout proposal has taken a central role in Obama’s stump speeches.

Clearly, the looming first presidential debate is the major factor in encouraging the top-ticket candidates to stay put. The debate, slated for Friday in Oxford, Miss., presents perhaps the biggest chance for either candidate to pull decisively ahead in the race and both are busy rehearsing.

Obama is scheduled to fly to Tampa, Fla., where he will stay until Friday morning to prepare for the debate. He has only one public event scheduled between now and then.

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McCain will travel to Ohio and Michigan to tour factories Tuesday, then to New York Wednesday to visit the United Nations and appear on David Letterman. McCain heads to Mississippi Wednesday night for debate prep.

Indeed, the Senate bailout vote could fall on Friday itself, creating a huge logistical headache for both candidates even to make sure they’re on stage when the curtain goes up at Ole Miss. Much less disciplined than the House, the Senate has a bad habit of delayed and ever-changing vote times.

But even without a high-pressure debate on the calendar, the candidates would be reluctant to take precious time away from campaigning with a mere 40-odd days left before Election Day.

Neither candidate trekked back to Capitol Hill to cast another important economic vote on July 26, when the Senate cleared a massive housing bill that aimed to shore up mortgage markets and prevent hundreds of thousands of foreclosures.

Biden, who had not yet been tapped as Obama's running mate, was there for the rare Saturday vote, voting “yea.”

Obama, however, did return to the Senate July 10 to vote in support of stalled Medicare legislation, which had failed on an earlier attempt to clear the 60-vote filibuster hurdle. Sen. Edward M. Kennedy, recently diagnosed with a brain tumor, also made a dramatic appearance to vote for the bill, which blocked a scheduled 10.6 percent cut in Medicare reimbursements for physicians.

The legislation passed, 69-30. McCain was the only “not present” on the Senate vote tally that day.

An Obama aide suggested that for the bailout, Obama would repeat that past pattern of returning for votes where the margin is close.